Lecture I: What is a wetland?

regulator definitions

Need for legally defensible language to provide binding frameworks for management

scientific definitions

Need to be flexible enough to encompass the domain of all situations that generate wetlands but specific enough to be relevant

Brinson 1993

"Such factors as water depth, flood duration, flow velocity, and water source either act as selective factors for the adaptations of organisms or are capable of performing work in the system."

Tiner 1999

"Wetlands are environments subject to permanent or periodic inundation or prolonged soil saturation sufficient for the establishment of hydrophytes and/or the development of hydric soils.. unless environmental conditions.. prevent them from forming"

problems with defining wetlands

1) Diverse Landscape Contexts; variability in context, structure, and function 2) Hydrologic Variability; the depth and duration of flooding can vary greatly among different wetlands and within any given wetland from year to year 3) Many Species are Not Restricted to Wetlands; wetland species range from those that require standard conditions to those that tolerate, not necessarily require, saturated conditions (ie. Acer rubrum, Larix laricina, Taxodium distichum) 4) Wetlands are "Ecotones"; boundaries around wetlands are arbitrary and transitional 5) Humans; modifications that create new wetlands and drainages or obscure indicators of naturally occurring wetlands

most comprehensive definition according to Mitsch and Gosselink

Cowardin et al. (1979): "Wetlands are lands transitional between terrestrial and aquatic systems where the water table is usually at or near the surface or the land is covered by shallow water. Wetlands must have one or more of the following.. 1) At least periodically the land supports hydrophytes; 2) The substrate is predominantly undrained hydric soils; and 3) The substrate is nonsoil and is saturated with water or covered by shallow water at some time during the growing season of each year."

cultural significance

Cyperus papyrus (primitive paper), Zizania sp. (wild rice, NY native, key food source historically to Native Americans of the Great Lakes region), Vaccinium macrocarpon (cranberry), Phragmites spp. (weaving, shelters in Middle East), Saggitaria latifolia (marsh potato, grows tubers, major food stock), Hierochloe odorata (sweetgrass, braided and weaved, native to Great Lakes Region), recreation

salient features of wetlands

Shallow water or saturated soil, all wetlands accumulate organic material and have unique soil conditions that differ from uplands, presence of organisms adapted to tolerate saturated conditions and absence of flood-intolerant organisms

Cowardin et al. definition

Uses hydrology and vegetation, introduces the term "undrained hydric soils," shifts focus to "one or more.."

Figure 2.2 Mitsch and Gosselink 2007

the three-component basis of a wetland definition: hydrology (water level/flow/frequency over time), physiochemical environment (soil, chemistry), and biota (vegetation, animals, microbes). From these components, the current approach to defining jurisdictional wetlands in the US is based on three indicators- hydrology, soils, & vegetation. Note that these three components are not independent and that there is significant feedback from the biota.